are they documents download from the IRS website or notices/letter you received in the mail? downloads can be saved as PDFs. actual letters/notices would need to be scanned, or picture taken with a cell phone. presently there is no way to attach documents to a return, they must be kept as an independent file. you could request an enhancement, but I doubt that you would get a positive response. In the decades I've used Turbotax, there has never been an option to attach a manual document to a tax return. In some cases, this required the taxpayer to file by mail. In other cases there is a special form (8453) which allows e-filing of the return and separate mailing of certain documents
saving online in in your account presents an issue in that in 7 years Turbotax will purge everything pertaining to that year. If you use online, you'll probably find that your 2017 return and documents are gone. The IRS also only saves documents and returns 7 years.
for permanent accessibility saving those items on your computer or in the cloud are your only options. if you save on your computer, you should make a backup and store on a separate device or in the cloud. hard drives go bad. There has been numerous posts from OP who had computer hard drive failure wanting to know how to retrieve returns and documents they had stored. The response was always something like if you didn't save a separate copy somewhere it's gone permanently.
